2018-06-29_PERMIT FILE - C1981025

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• Undisturbed Soil Sampling and Mapping At the request of the Division, additional soil sampling and mapping was done at the mine site in 1981. Results of laboratory analyses are given in Table 3.8.1-2. Samples were collected in the manner pre- viously described and analyzed by the C.S.U. Soils Testing Lab in Ft. Collins. Sample locations are shown on the Mine Area Soils Map, Drawing D-3-14 Map units shown on this map are described below. Map Unit Descriptions 18E. Typic Argiborolls complex, 25 to 65 percent slopes. These steep to very steep soils are on mountain sideslopes at elevations of 7,600 to 9,000 feet. The two components of this mapping unit are clayey- skeletal, montmorillonitic, Typic Argiborolls, 55 percent, and fine, montmorillonitic, Typic Argiborolls, 45 percent. These soils occur on the south facing portion of the ridge along the vent pipe road corri- dor. About 10 percent of the unit is soils that have coarser • textures. Both soils are moderately deep to deep and formed in colluvium and residuum from interbedded sandstone and shales. Typically, the clayey-skeletal Argiboroll soil is very dark grayish brown, very cobbly clay about 16 inches thick. Depth to bedrock ranges from 20 inches to more than 40 inches. The fine Argiboroll soil typically has a dark brown cobbly loam surface layer about 8 inches thick. The upper part of the subsoil is dark brown cobbly clay loam about 4 inches thick. The lower part is brown clay about 14 inches thick. The substratum is brown cobbly clay loam about 12 inches thick. Depth to bedrock ranges from 20 inches to more than 40 inches. Permeability of these soils is slow. Effective rooting depth is 20 inches to more than 40 inches. Available water capacity is 0.10 to 0.16 in./in. Surface runoff is high. Topsoil suitability is poor due • to the amount of coarse fragments in the dominant soil and steep slopes. 3-104